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      <title>使用ExecutorService进行异步任务调度 - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>使用ExecutorService进行异步任务调度 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
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                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
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                    <div id="hint-container" class="hint-container"></div>
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                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
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      <script>
        const quizData = [
  {
    "question": "在Java的ExecutorService中，`submit()`方法和`execute()`方法的主要区别是什么？",
    "options": [
      "`execute()`用于执行Callable任务，而`submit()`用于执行Runnable任务。",
      "`submit()`可以返回一个Future对象来获取任务结果或状态，而`execute()`没有返回值。",
      "`execute()`会立即执行任务，而`submit()`会将任务放入队列等待执行。",
      "`submit()`只能用于单线程执行器，而`execute()`可以用于任何类型的线程池。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`submit()`方法用于提交需要返回结果的任务（Callable）或不需要返回结果的任务（Runnable），它会返回一个Future对象，调用者可以通过这个对象与任务进行交互，例如获取结果、取消任务。而`execute()`方法只能接受Runnable任务，并且是“即发即忘”的模式，它没有返回值，无法获取任务的执行状态或结果。",
    "source": "文档中「4. 提交任务给线程池」部分",
    "hint": "文档提到，一个方法返回`Future`对象，而另一个则没有返回值。思考一下`Future`的作用是什么。"
  },
  {
    "question": "当你需要关闭一个`ExecutorService`，但又希望确保所有已经提交的任务都能执行完毕，应该调用哪个方法？",
    "options": [
      "`shutdownNow()`",
      "`cancel(true)`",
      "`shutdown()`",
      "`close()`"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`shutdown()`方法会启动线程池的平滑关闭流程。它会拒绝接收任何新的任务，但会继续处理任务队列中所有已存在的任务。与之相对的`shutdownNow()`方法会尝试立即停止所有正在执行的任务，并返回队列中尚未开始执行的任务列表。",
    "source": "文档中「6.1 shutdown()方法」部分",
    "hint": "文档中对比了两种关闭线程池的方法，一种是“优雅地”关闭，另一种是“立即”停止。"
  },
  {
    "question": "根据文档，如果你需要创建一个线程池，它的线程数量会根据任务量的增减而动态调整，并且会自动回收空闲超过60秒的线程，应该使用`Executors`类的哪个静态方法？",
    "options": [
      "`Executors.newFixedThreadPool(int nThreads)`",
      "`Executors.newSingleThreadExecutor()`",
      "`Executors.newCachedThreadPool()`",
      "`Executors.newScheduledThreadPool(int corePoolSize)`"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`Executors.newCachedThreadPool()`会创建一个缓存线程池。这种线程池会根据实际需要创建新线程来执行任务，如果之前创建的线程可用，则会重用它们。空闲时间超过60秒的线程会被终止并从缓存中移除，从而实现动态调整和资源回收。",
    "source": "文档中「3.2 创建一个缓存线程池」部分",
    "hint": "文档描述了一种“缓存”机制的线程池，它能够根据需要创建和回收线程。"
  },
  {
    "question": "在使用`ExecutorService.submit()`提交任务后，返回的`Future`对象的核心作用是什么？",
    "options": [
      "用于配置线程池的核心参数，如线程数和队列大小。",
      "直接执行异步任务的逻辑代码。",
      "代表一个异步计算的结果，并提供了检查任务状态、获取结果和取消任务的方法。",
      "用于创建新的线程来执行后续任务。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`Future`对象是一个占位符，它代表了一个未来某个时间点会完成的异步操作的结果。通过`Future`，我们可以查询任务是否完成（`isDone()`），阻塞并等待其完成以获取结果（`get()`），或者尝试取消任务的执行（`cancel()`）。",
    "source": "文档中「5. 使用Future获取任务执行结果」部分",
    "hint": "思考一下“Future”这个词的含义，它代表了未来的某个结果。"
  },
  {
    "question": "如果需要安排一个任务在延迟5秒后执行，并且之后每10秒重复执行一次，应该使用哪个`ExecutorService`的子接口及其方法？",
    "options": [
      "`ThreadPoolExecutor`的`execute()`方法配合`Thread.sleep()`",
      "`ScheduledExecutorService`的`scheduleAtFixedRate()`方法",
      "`ExecutorService`的`submit()`方法",
      "`ScheduledExecutorService`的`schedule()`方法"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`ScheduledExecutorService`接口专门用于处理延迟和周期性任务。`scheduleAtFixedRate()`方法可以安排一个任务在指定的初始延迟后开始执行，并以固定的频率（周期）重复执行。而`schedule()`方法只执行一次延迟任务。",
    "source": "文档中「7. 使用ScheduledExecutorService进行定时任务调度」部分",
    "hint": "文档中有一个专门的章节讲述如何执行“定时”和“周期性”的任务。"
  },
  {
    "question": "调用`Future.get()`方法时，可能会发生什么情况？",
    "options": [
      "如果任务尚未完成，该方法会立即返回`null`。",
      "该方法会阻塞当前线程，直到异步任务执行完成并返回结果。",
      "该方法会立即返回任务的当前执行进度百分比。",
      "该方法总是立即返回，无论任务是否完成。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`Future.get()`方法的设计目的是获取异步任务的最终结果。如果任务在调用`get()`时还未完成，那么调用线程将被阻塞，直到任务执行完毕。这是同步等待异步结果的关键机制。",
    "source": "文档中「5.1 获取任务结果」部分",
    "hint": "文档中明确指出，这个方法会“阻塞”，直到任务完成。"
  },
  {
    "question": "根据文档中关于性能优化的建议，为CPU密集型任务选择线程池大小时，一个常见的参考依据是什么？",
    "options": [
      "设置为一个固定的较大值，例如100。",
      "设置为与提交的任务总数相等。",
      "基于当前系统的可用CPU核心数。",
      "总是使用`newSingleThreadExecutor`以避免线程切换开销。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "为了最大化CPU的利用率并减少不必要的线程上下文切换开销，对于CPU密集型任务，通常建议将线程池的大小设置为与CPU核心数相当。文档中给出的示例代码是 `Runtime.getRuntime().availableProcessors()`，这正是获取可用CPU核心数的方法。",
    "source": "文档中「8.1 合理选择线程池大小」部分",
    "hint": "文档建议线程池的大小应该基于硬件资源，特别是与计算能力最相关的那个部件。"
  }
];
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          optionsListEl.innerHTML = '';
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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<h2>答题报告</h2>' +
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                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
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            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  